best sub to match SF olympica 3

czechu82

You’ve got some nice fast bass drivers in the SF’s with the 2 x 7" W18XTR drivers, driven by fast tight amps in the Ref 600’s.
The last thing you want is to mate it with a slow 15"-18" subwoofer meant for HT.
  
Look for well reviewed fast musical subs with I would say 2 x 10" to mate up with the SF’s 7"s, that may have "motional feedback" to keep them tight.
Because they’re meant to keep up with the ML ESL’s they should be fast.
Martin Logan BalancedForce 210 have 2 x 10" in each box, get two of them so your not monoizing the bass.

http://www.theabsolutesound.com/articles/martinlogan-balanced-force-210-subwoofer/

Cheers George

If you are not going to use a high pass filter don’t waste your money on a sub with that option. I use my sub with the main speakers running full range without using a high pass filter! If you are going to use a high pass filter you should check out the higher priced JL E subs!

Here is a review!
www.theabsolutesound.com/articles/jl-audio-e-sub-e110-subwoofer/

I use the JL Audio E-110 supporting my Oly 3's, using the high pass feature with excellent results.  I could add a second sub, but don't feel it's necessary.  The 'leap of faith' required to insert a $1500 sub between $20k worth of amplification and $13.5k in speakers is not a small 'leap', but once you try it and dial in the sub you should be pleased with the results.  JL Audio's tech support team will spend as much time on the phone with you as necessary to help tune the sub for optimum results.